@color: blue;
@font:50px;
.a{
    width: 80px;
    height: 80px;
    margin: auto auto;
    background-color: #f00;
    border: 1px solid #f00;
    .b{
        height: 70px;
        width: 70px;
        margin: auto auto;
        background-color: #f91;
        a{
            color: aliceblue;
            &:hover{
                font-size: @font;
                color: @color;
            }
        }
    }
}